Memory mechanism A variation in a part of the brain may explain why some people have a better memory of reality than others and could advance understanding of brain disorders like schizophrenia, say scientists.

In a study published in the Journal of Neuroscience , researchers from Cambridge University tested a group of volunteers and found differences in their ability to distinguish between real or imagined memories.

The scientists then found a direct link between these results and the size of a specific area of the brain called the paracingulate sulcus, or PCS.

The PCS is one of the last regions of the brain to develop before birth, and the study found that people with a larger PCS were better at discerning real experiences from imagined ones.

"The memory differences we observed were quite striking. It is exciting to think that these individual differences in ability might have a basis in a simple brain folding variation," says Dr Jon Simons of Cambridge University , who led the research.

The findings may also help scientists understand more about schizophrenia, he says, because an inability to recognise what is real and what isn't is a hallmark of the disease.

"Hallucinations are often reported whereby, for example, someone hears a voice when nobody's there. Difficulty distinguishing real from imagined information might be an explanation for such hallucinations," says Simons. "The person might imagine the voice but misattribute it as coming from the outside world."

Schizophrenia is a severe mental disorder which affects 24 million people worldwide, according to World Health Organization data, yet relatively little is known of its causes.

"We've found evidence that suggests this particular (brain) region might be reduced in people with schizophrenia, and that this could be the beginning of an explanation for why these people experience hallucinations," says Simons.

Recognising pairs

The 53 volunteers in the study first had brain scans which showed whether they had a clear presence or absence of PCS in the left or right brain.

The researchers then showed them well-known word pairs, such as 'Laurel and Hardy', which were sometimes complete and sometimes had the second word blanked out.

The volunteers were then asked to remember whether they had seen a completed pair, or whether they had completed the pair in their own mind.

"What we're interested in linking next is whether individuals with schizophrenia who also have that reduction in the PCS are definitely more likely to experience hallucinations," says Simons, adding that his team is planning further research in the coming months.